101-84-8 Diphenyl ether

The diphenyl ether nitrofen (1) [24], introduced in 1963 by Rohm and Haas, now Dow AgroSciences the oxadiazolinone oxadiazon (2) [25, 26] (Explorer , Herbstar , Romax , Ronstar ), introduced in 1968 by Rhone-Poulenc and the tetrahydrophthalimide chlorophthalim 3 [27], introduced in 1972 by Mitsubishi, represent the earliest examples of Protox herbicides (Fig. 3.2). Though all three classes are chemically quite different, they share a common mode of action, inhibition of the protoporphyrinogen oxidase enzyme, though this was not known until the late 1980s. 

Each of these chemistries generated intensive work in the 1960s-1980s, which resulted in numerous diverse chemistries, from which several useful commercial products were obtained. 

Following the discovery of the herbicidal activity of nitrofen (1) in 1963, intense research by several agrochemical companies resulted in a vast number of highly active and diverse chemistries [28, 29]. As mentioned earlier, the diphenyl ether chemistry represents the first class of Protox herbicides. Replacement of the aromatic 4-chloro group with a trifluoromethyl, as is the case with oxyfluorfen (5) (Goal ) [30], resulted in a significant improvement in biological activity, and 2- 

The extensive research invested by many companies in this third generation of diphenyl ether chemistry resulted in many active molecules, but no successful commercial product. 

Several discoveries made in the 1960s had a significant impact on our understanding of the structure-activity of Protox herbicides. The first breakthrough was the discovery of the importance of the 2,4-dihalo-5-substituted-phenyl substitution pattern. Rhone-Poulenc first introduced 3-(2,4-dichlorophenyl)-l,3,4-oxadiazol-2(3H)-one (9) in 1965 [40]. Further structure-activity optimization at the phenyl ring soon led to the discovery in 1968 of the 2,4-dichloro-5-isopropoxyphenyl substitution pattern of the herbicide oxadiazon (2) [41, 42]. 

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CUCI2 on phenyl magnesium halides also provide reasonable quantities of diphenyl. Uses include its action as a fungistat during shipment of apples and oranges, and as a heat transfer agent (dowtherms) mixed with diphenyl ether and terphenyls. 

The following liquids may be used (boiling points are given in parentheses) — chlorobenzene (132-3°) bromobenzene (155°) p cymene (176°) o-dichloro-benzene (180°) aniline (184°) methyl benzoate (200°) teti-alin (207°) ethyl benzoate (212°) 1 2 4-trichlorobenzene (213°) iaopropyl benzoate (218°) methyl salicylate (223°) n-propyl benzoate (231°) diethyleneglycol (244°) n-butyl benzoate (250°) diphenyl (255°) diphenyl ether (259°) dimethyl phth ate (282°) diethyl phthalate (296°) diphenylamine (302°) benzophenone (305)° benzyl benzoate (316°). 

Purely aromatic ethers e.g., diphenyl ether), which are commonly encountered, are very hmited in number. Most of the aromatic ethers are of the mixed aliphatic - aromatic type. They are not attacked by sodium nor by dilute acids or alkahs. When hquid, the physical proper-ties (b.p., d . and ) are useful constants to assist in their identification. Three important procedures are available for the characterisation of aromatic ethers. 

Ethers. Di-re-butyl ether Anisole Diphenyl ether. 

The cyclized products 393 can be prepared by the intramolecular coupling of diphenyl ether or diphenylamine(333,334]. The reaction has been applied to the synthesis of an alkaloid 394[335]. The intramolecular coupling of benzoyl-A-methylindole affords 5-methyl-5,10-dihydroindenol[l,2-b]indol-10-one (395) in 60% yield in AcOH[336]. Staurosporine aglycone (396) was prepared by the intramolecular coupling of an indole ring[337]. 

Brominated Diphenyl Oxides. Brominated diphenyl oxides are prepared by the bromination of diphenyl oxide. They are often referred to as diphenyl ethers. Taken together, the class constitutes the largest volume of brominated flame retardants. They range ia properties from high melting sohds to hquids. They are used, as additives, ia virtually every polymer system. 

Electron Transport Between Photosystem I and Photosystem II Inhibitors. The interaction between PSI and PSII reaction centers (Fig. 1) depends on the thermodynamically favored transfer of electrons from low redox potential carriers to carriers of higher redox potential. This process serves to communicate reducing equivalents between the two photosystem complexes. Photosynthetic and respiratory membranes of both eukaryotes and prokaryotes contain stmctures that serve to oxidize low potential quinols while reducing high potential metaHoproteins (40). In plant thylakoid membranes, this complex is usually referred to as the cytochrome b /f complex, or plastoquinolplastocyanin oxidoreductase, which oxidizes plastoquinol reduced in PSII and reduces plastocyanin oxidized in PSI (25,41). Some diphenyl ethers, eg, 2,4-dinitrophenyl 2 -iodo-3 -methyl-4 -nitro-6 -isopropylphenyl ether [69311-70-2] (DNP-INT), and the quinone analogues,... 

Herbicides can be grouped according to common stmctural features. Sometimes the assignment is arbitrary when there are a multitude of functional groups, eg, acifluorfen which is a diphenyl ether (phenoxy compound) as well as a trifluoromethyl compound. 

Researchers at Du Pont used hydroquinone asymmetrically substituted with chloro, methyl, or phenyl substituents and swivel or nonlinear bent substituted phenyl molecules such as 3,4- or 4,4 -disubstituted diphenyl ether, sulfide, or ketone monomers. Eor example,... 

Colorless dyes of the chlorinated diphenyl ether—ureasulfonic acid type (Mitin [3567-25-7] (158)) and the (polychloro-2-chloromethylsulfonamido)-diphenyl ether type (Eulan (159)) appHed at 1—3% of the fabric weight are the most widely used during the fabrication of woolens. They cannot be removed by dry cleaning and provide protection from fabric pests over the lifetime of the product. 

Reaction of bis (sulfonyl chloride)s with diaryl ether produces polyethersulfones. For example, condensation of diphenyl ether with the disulfonylchloride of diphenyl ether yields polyethersulfone (5) ... 

Other Synthesis Routes. Several alternative routes to the nucleopbilic substitution synthesis of polysulfones are possible. Polyethersulfone can be synthesized by the electrophilic Eriedel-Crafts reaction of bis(4-chlorosulfonylphen5l)ether [121 -63-1] with diphenyl ether [101-84-8] (11—13). 

Specialty sulfonic acid-based surfactants make up a rather large portion of surfactant production in the United States. Approximately 136,000 metric tons of specialty sulfonic acid-based surfactants were produced in 1992, which included alpha-olefin sulfonates, sulfobetaines, sulfosuccinates, and alkyl diphenyl ether disulfonates (64). These materials found use in the areas of household cleaning products, cosmetics (qv), toiletries, emulsion polymerization, and agricultural chemical manufacture. 

SuIfona.tlon, Sulfonation is a common reaction with dialkyl sulfates, either by slow decomposition on heating with the release of SO or by attack at the sulfur end of the O—S bond (63). Reaction products are usually the dimethyl ether, methanol, sulfonic acid, and methyl sulfonates, corresponding to both routes. Reactive aromatics are commonly those with higher reactivity to electrophilic substitution at temperatures > 100° C. Tn phenylamine, diphenylmethylamine, anisole, and diphenyl ether exhibit ring sulfonation at 150—160°C, 140°C, 155—160°C, and 180—190°C, respectively, but diphenyl ketone and benzyl methyl ether do not react up to 190°C. Diphenyl amine methylates and then sulfonates. Catalysis of sulfonation of anthraquinone by dimethyl sulfate occurs with thaHium(III) oxide or mercury(II) oxide at 170°C. Alkyl interchange also gives sulfation. 

Substitution at the 3 and 5 positions with alkyl groups or with halogens large enough to force the diphenyl ether nucleus to adopt a minimum... 

In the first synthesis of T, the diphenyl ether was formed from -methoxyphenol and 3,4,5-triiodonitrobenzene. The nitro group was replaced by a nitril which was then built up into the alanyl side chain by a series of steps (10). 

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